The chromosomal map position status of conditional lethal (ts) mutants of Bacillus subtilis 168 selected in this laboratory will be assessed utilizing transformation data fromdensity transfer experimentsand membrane enrichement i index determinations. In particular, conditional markers located in the region of the chromosome replication origin and terminus are sought. The position of conditional markers relative to known genetic cmarkers may be examined by cotransformation or cotransduction. Conditional mutants defective in aspects of chromosome replication will also be studied.